Flashcards in Topic 4a - Cellular reproduction Deck (51):
Prokaryotic cells divide how?
sections of DNA that code for one product (protein)
uncondensed DNA - typical form in the cell
Condensed form of DNA - easily divided evenly
Place in order from DNA double helix to chromosome...
DNA double helix -> DNA wound around histone proteins -> coiled DNA/histone beads -> coiled & looped DNA attached to protein scaffold -> folded chromosome
Ends of chromosomes are called...?
Centre of chromosome...?
centromere - links sister chromatids
How many chromosomes in a male?
23 (22 + X&Y)
In mitosis, what are the stages of interphase? Briefly describe each stage...
G1: cell growth & differentiation
S: synthesis of DNA; chromosomal duplication
G2: cell growth & preparation for cell division
What are the phases of mitotic cell division...?
telophase & cytokinesis
Describe the events in early & late prophase...
Early prophase - chromosomes condense; spindles begin to form; nuclear membrane begins to disappear
Late prophase - centrioles move to opposite poles; spindle microtubules attach to centromeres forming kinetochores; nucleolus & nucleus have almost disappeared
Describe the events in metaphase...
chromosomes & their centromeres attached to spindle fibres are lined up in the middle of the cell
Describe the events in early & late anaphase...
Early anaphase - centromeres split; half of the chromosomes move to one pole, half to the other pole
Late anaphase - chromosomes almost at respective poles; cell membrane begins to pinch at the center
Describe the events in telophase...
cell membrane completes constriction; chromosomes extend; nuclear envelope begins re-forming
cytoplasm divides; parent cell becomes 2 daughter cells (diploid) with identical genetic information
Where are the 3 check points in cell division?
G1 -> S: is DNA intact & suitable for replication?
G2 -> M: DNA completely & accurately replicated?
metaphase -> anaphase: are all chromosomes attached to the spindle & aligned at the equator?
In cell differentiation, what are the 3 types of cells...? Give examples of each...
stem cells - give rise to other stem cells & other types of cells eg. stem to stem, & stem to neuron
other cells capable of dividing - give rise to only the same type of cell
fully differentiated cells - incapable of dividing eg. neuron cannot divide
two complete sets of every gene (chromosomes) 2n chromosomes
Define allele. Give example
alternate forms of the same gene
eg. eye colour (brown or blue) both alleles code for 'eye colour'
T or F - homologous chromosomes can have different alleles?
Define sexual reproduction
combining genetic material from two organisms (same species)
If offspring contain genetic material from two parents, how do we avoid repeated doubling of genetic material each generation?
fusion of gametes (each containing n chromosomes)
Parental cells contain how many sets of chromosomes? (diploid or haploid?)
Gametes are diploid or haploid?
Fertilised egg is diploid or haploid?
From 2n chromosomes, mitosis produces how many chromosomes?
Somatic cells (non-sex cells) are...?
Sex cells are...?
What happens in prophase I of meiosis?
What happens at metaphase I of meiosis?
homologue chromosomes align in the center of the cell
What are the sections of crossing over called?
What happens at anaphase I of meiosis?
mitotic spindles pull homologous chromosomes to opposite poles
Analogous to mitosis is...?
What are the sources of genetic variability?
- random shuffling of homologous chromosomes (2^23 = >8 million combinations)
- crossing over
- fusion of gametes (8 million x 8 million = 64 trillion unique combinations)
Haploid life cycle occurs in...?
protists, algae, fungi
Diploid life cycle occurs in...?
Alternation of generations occurs in...?
specific position of a gene or DNA sequence on a chromosome
stable & inheritable change in nucleotide sequence
set of 1 maternal & 1 paternal chromosome that pair up inside a cell during meiosis
repetitive nucleotide sequences at each end of a chromatid - protects chromosome from deterioration or fusion with other chromosomes
one copy of a duplicated chromosome joined by a centromere
complete set of chromosomes in the nucleus of a eukaryotic cell
a chromosome that is NOT a sex chromosome
Define sex chromosome...
allosome - haploid
organise mitotic spindles
completion of cytokinesis
protein structure on chromatids where spindle fibres attach during cell division to pull sister chromatids apart
cell division into two genetically identical daughter cells
cell division necessary for reproduction in eukaryotes such a animals, plants, and fungi.